1. Field of the Invention
The present invention relates to the termination of telephone calls in a telephone network that provides a privacy screening service to its subscribers.
2. Background of the Invention
A privacy screening service is a service that allows a subscriber to the privacy screening service to screen incoming calls. The privacy screening service provides information to the called party (in this case, the subscriber to the privacy screening service) that allows the subscriber to make an informed decision as whether or not to answer the call. For example, a subscriber may use the privacy screening service to block all unidentified calls from going through. Private telephone numbers are telephone numbers that block services such as “caller ID” that would otherwise identify the caller to the called party. In telephone systems that offer private numbers and a privacy screening service to its customers, calls from a private number to a subscriber with the privacy screening service cannot be completed automatically, unless the caller authorizes the system to override the privacy of his number.
FIG. 1 is a schematic diagram showing the basic architecture of an Advanced Intelligent Network telephone system. The Advanced Intelligent Network System is described in U.S. Pat. No. 5,701,301 and U.S. Pat. No. 5,838,774, which are hereby incorporated by reference. FIG. 1 shows the caller's telephone 101 which is connected via the calling party's voice line 102a to its Service Switching Point (SSP) 103. SSP 103 is connected via voice trunk 102b to a second SSP (SSP 104). SSP 104 is the SSP that services the called party's telephone 105. In this example, the called party is a subscriber who has subscribed to the privacy screening service. (The called party will also be referred to as the “subscriber” as well as the “called party” herein.) FIG. 1 also shows a Signaling Transfer Point (STP) 106 which services a Service Control Point (SCP) 107 and a third SSP (SSP 108) which services a Service Node (SN) 109. SCP 107 has a database 107a that contains subscriber information.
STP 106 is a signaling hub that routes packets of data over the common channel signaling network. Common channeling signaling networks are data communications networks laid over the system's switching network that carry data and control messages to and from and among the SSPs, STPs, and SCPs in the network. Signaling System 7 (SS7) is the protocol that runs over common channel signaling networks. A common channel signaling network using the Signaling System 7 protocol is often referred to as an SS7 network. The SS7 network carries data and control messages to the SSPs in the telephone network. SCPs are powerful fault-tolerant computers, e.g., AT&T Star Server FT Model 3200 or AT&T Star Server FT Model 3300 computers (these and more current computers such as the Advantage P200 and Advantage 4P200 models are presently available from Lucent Technologies). SCPs are “intelligence centers” with access to applications databases that enable the network to deliver advanced services such as caller ID, privacy screening and call forwarding. The SCPs also execute service package applications (SPAs) that deliver the advanced services. SNs arc physically generally similar to SCPs, but include voice and Dual Tone Multi-Frequency (DTMF) signal recognition circuits, voice synthesizers, and voice recognition and digit collection capabilities. The operators of the telephone network can program their SNs to manage data, to respond to calls and to route calls as specified by the telephone network, and to collect digits from a caller or subscriber. The SN's voice circuits can also be programmed to provide a voice response (e.g., to play pre-selected announcements) to callers and to perform voice recognition. SNs can also be programmed to respond to input from the callers by, e.g., further routing the call.
As shown in FIG. 1, STP 106 controls communications between SSPs 103, 104 and 108 and SCP 107. The SSPs are connected to the caller's and the subscriber's telephones and to each other via voice lines 102a and 102c and via voice trunks 102b and 102d. The SSPs communicate with STP 106 and SCP 107 via SS7 data links 110a, 110b, 110c and 110d. SN 109 is connected to SSP 108 by an Integrated Service Digital Network (ISDN) Basic Rate Interface (BRI) line 111.
When the caller places a call to the subscriber, the call is routed by SSP 103 to SSP 104. FIG. 1a shows a prior art system in which call 1 is routed from the caller to SSP 103 and then to SSP 104. Because the subscriber has subscribed to the privacy as screening service, that call (like all calls to that subscriber's number) triggers a “termination attempt trigger” or TAT. In response to the TAT, SSP 104 issues query 2, shown in FIG. 1a. Query 2 is a message that goes up to SCP 107 via STP 106 asking for directions as to how the call should be terminated. The query includes the following information: the subscriber's telephone number (in the called party field), the calling party's telephone number (in the calling party field), the calling party's presentation restriction indicator (also in the calling party field), and, optionally, the trigger criteria type (indicating the service for which the query is intended).
SCP 107 checks the presentation indicator in the calling party field of the query received as a result of the termination attempt trigger. If presentation of the caller's number is not restricted, i.e., if the caller's number is public, SCP 107 sends back a response (response 3 in FIG. 1a) instructing SSP 104 to terminate the call, and to supply the caller's telephone number (and, if the subscriber has subscribed to a higher level of service such as caller ID deluxe, the caller's name and telephone number). In that case, SSP 104 terminates the call (call 1′ in FIG. 1a), i.e., completes the call, supplying the subscriber with the caller's number (and possibly also with the caller's name). If the caller's name is to be supplied to the customer, SSP 104 launches another query, a TR1188 CNAM query to the SCP, to obtain the caller's name from either database 107a or another database on the system that contains the names corresponding to the telephone numbers.
The prior art system of FIG. 1a asks the calling party to record his or her name whenever the calling party number is private or unknown. In this prior art system, if the caller's number is private or unknown, SCP 107 enters the subscriber's number in the calling party field in response 3 and directs SSP 104 to forward the call to SN 109 (call 1″ in FIG. 1a). When SN 109 answers the call, it asks the calling party to record his or her name. If the calling party responds by recording his or her name, SN 109 then calls the subscriber (call 4 in FIG. 1a), using the subscriber's telephone number (that had been stored in the calling party field).
The TAT provisioned on the subscriber's line at SSP 104 triggers a second time, sending a query (query 5) up to SCP 107 through STP 106. SCP 107 recognizes that this call originated with a service node, SN 109, and sends a response (response 6 in FIG. 1a) authorizing termination to the subscriber. SN 109 then plays a dialog to the subscriber, identifying the calling party by playing the calling party's recorded name for the subscriber. If the subscriber chooses to accept the call, the call is put through (leg 4′ of call 4 in FIG. 1a). If the subscriber refuses to accept the call, the calling party is informed that his or her call was not accepted, and the call is disconnected.
This prior art system works irrespective of whether the calling party number is public (i.e., not private), private or unknown, but cannot take full advantage of the advanced intelligent network capabilities of the AIN system, because the calling party number is not preserved. Thus this prior art system does not allow the use of advanced intelligent network features such as call return or call trace.